Rear bumper for an automobile



FIG. 1 is a front perspective view of a rear bumper for an automobile of our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side view thereof; and,

FIG. 6 is a left side view thereof. 

The ornamental design for a rear bumper for an automobile, as shown and described. 